In a new BBC documentary, Mind Over Marathon, a film about 10 people who suffer from mental health issues and are training to run a marathon, William says that his mother's death still affects him two decades later.

“The shock is the biggest thing I still feel, 20 years later, about my mother,” William says. “People think shock can’t last that long, but it does. It’s such an unbelievably big moment in your life and it never leaves you; you just learn to deal with it.”

Though he recently went back to Paris for the first time, William apparently has yet to visit the site of his mother's death. And who can blame him? Her story is as haunting as it is heartbreaking.